The present invention relates to a gas-fired humidifier.
Previous such constructions involve the passage of hot gases through generally horizontal tubes which extend through a tank of water, the water thereby being boiled to produce steam.
Such a construction is not very efficient.
The present invention seeks to improve the efficiency of gas-fired humidifiers.
Accordingly, the present invention is directed to a gas-fired humidifier comprising a heat exchanger with a plurality of generally upwardly extending tubes connected at their lower ends to a source of water and at their upper ends to a steam header, and a gas-fired burner arranged to direct heat to the exterior of the tubes so as to cause water therein to boil and form steam in the steam header.
Such an arrangement has the advantage that airlocks are unlikely to form in the tubes.
Preferably, the burner projects heat in a generally horizontal direction across the tubes.
The efficiency with which heat is transferred is further improved if the burner is provided with a diffuser plate, in front of which is located a flat mesh bed.
Preferably, the tubes are more closely spaced from one another in a first region than they are in a second region which is further away from the burner than the said first region.
Preferably, the tubes nearer the burner are made of a material having a lower heat conductivity than the tubes which are further from the burner.
Preferably, the tubes which are nearer the burner are not finned or have a relatively small amount of fin material, whereas the tubes further from the burner are provided with fins or have a larger amount of fin material.
The tubes which are nearer the burner may be flanked with water jackets which are also connected at their lower ends to a said source of water and at their upper ends to the steam header.
In this way it will be seen that the ease with which heat is transferred from the flame or hot gases ejected by the burner is greater at positions further away from the burner to compensate for the drop in temperature of the flame or hot gases in those regions.